What is the interaction between rifampin and oral contraceptives?

• A. No interaction with oral contraceptives.
• B. Oral contraceptives increase Rifampin clearance.
• C. Rifampin induces hepatic enzymes, reducing OC effectiveness.
• D. Rifampin has a mild interaction with oral contraceptives.

Answer: (C)

Rifampin is a strong inducer of liver drug-metabolizing enzymes, which speeds up the breakdown of oral contraceptives. It mainly activates enzymes like CYP3A4 and related pathways, increasing the clearance of the hormones in birth control pills (the estrogen and progestin components). When these hormone levels drop faster, the pills’ ability to suppress ovulation diminishes, raising the chance of breakthrough ovulation and unintended pregnancy.

Because enzyme induction takes time to develop and lasts for a while after rifampin is stopped, this interaction is clinically important during therapy and for a period afterward. In practice, women on rifampin should use an alternative or nonhormonal method of contraception, or at least rely on a backup method, during treatment and for some time after finishing rifampin to ensure contraception remains effective.

Why the other statements don’t fit: it’s not a matter of no interaction, and rifampin does not increase OC levels; it reduces them by accelerating metabolism, and the interaction is more than mild.